The ubiquitin/proteasome pathway (UPP) plays a central role in the selective degradation of intracellular proteins. The translational research that we propose addresses UPP-regulated mechanisms that can be manipulated to increase neuroprotection and/or neuronal recovery following CNS injuries. There is an obvious gap in the knowledge of these UPP-regulated mechanisms. The main goal of this application is to characterize molecular mechanisms regulated by the UPP that are neuroprotective and promote neurite outgrowth following CNS injury. To characterize these UPP-regulated pathways, two of the UPP steps will be manipulated: (1) Proteasorne activity by pharmacological and more specific genetic approaches and (2) Ubiquitination by overexpressing a ubiquitin ligase that promotes neurite outgrowth. The effect of these UPP manipulations will be investigated in human neuroblastoma SK-N-SH cells as well as in rat dorsal root ganglion and cortical neurons grown in the presence of axonal regeneration inhibitors. Through molecular, biochemicaland immunocytochemical analyses we will assess the effects of the UPP-manipulations on the Rho family of small GTPases, on the putrescine-producing enzyme ornithine decarboxylase (ODC), and on the expression of the neuron-specific ubiquitin hydrolase, UCH-L1. Our working hypothesis is that the UPP-manipulations will (1) affect the levels of Rho proteins, which will in turn enhance neurite outgrowth, as Rho proteins are key players in preventing CNS neurite outgrowth and axonal regeneration, (2) enhance ODC levels causing a rise in putrescine, which in turn will block the effect of myelin inhibitors on neurite outgrowth, and (3) alter the levels of UCH-L1, which facilitates the use and reuse of ubiquitin molecules, a process that will regulate the turnover of proteins relevant to CNS neurite outgrowth and axonal regeneration. This project draws on the unique combination of skills and expertise of our groups on the UPP (Figueiredo-Pereira) and axonal regeneration (Filbin). We expect our results to be applicable to treatment-of neurological conditions that involve neuronal damage, such as stroke, neurodegenerative disorders and spinal cord injury. Relevance to Public Health: Our research addresses mechanisms that can be manipulated to increase neuroprotection and/or neuronal recovery following neurological conditions such as stroke, spinal cord injury! and Alzheimer's disease. It is particularly relevant to health disparities as, for example, African-Americans: and Hispanics of both genders have a higher death rate due to stroke than White Americans. The aging: population of African-Americans and Hispanics presents a particular challenge, as older adults who havei had a stroke have a higher risk of developing neurodegenerative disorders such as Alzheimer's disease. expect that our translational research will identify new targets for effectively treating CNS injury.